Updated GitHub action to run on Ubuntu 20.04.

Author: orbitalquark

.github/workflows/release.yml

@@ -5,7 +5,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     container: ghcr.io/orbitalquark/textadept-build:v2.0
     steps:
       - name: Checkout textadept
@@ -22,18 +22,6 @@ jobs:
         uses: actions/checkout@v2
         with:
           path: textadept/modules/file_diff
-      - name: Git init if necessary
-        shell: bash
-        run: |
-          # If git version is less than 2.18, a git clone will not be made in
-          # this container. In that case, make a temporary repository so
-          # "make release" can archive the repo's contents for release.
-          if [[ -d .git ]]; then exit 0; fi
-          git init
-          git add .
-          git config --global user.email "none@example.com"
-          git config --global user.name "none"
-          git commit -m 'none'
       - name: Build
         shell: bash
         run: |